I am using an application that sends requests like this to elasticsearch 5 (Kibana 3):
http://localhost:9200/twitter/_aliases?ignore_unavailable=true&ignore_missing=true
The response from es5:
{"error":{"root_cause":[{"type":"illegal_argument_exception","reason":"request [/twitter/_aliases] contains unrecognized parameter: [ignore_missing]"}],"type":"illegal_argument_exception","reason":"request [/twitter/_aliases] contains unrecognized parameter: [ignore_missing]"},"status":400}
When sent to an es2 instance, the response is valid.
I already stumbled upon a few GitHub issues and found that this troublemaking option (ignore_missing) was removed a long time ago but since then ignored.
GitHub: ignore_missing removed from _aliases
GitHub: Revisit indices options and make default values consistent
All I need to know now if es5 purposely responds with an error or if I'm doing something wrong.